Paint stripping method



Jan. 25, 1966 D, M. EVANS ETAL PAINT S'I'RIPPING METHOD 2 Sheets-Sheet 1 Original Filed Sept. 5, 1959 a m m M J W Jan. 25, 1966 D. M. EVANS ET AL 3,231,424

PAINT STRIPPING METHOD Original Filed Sept. 5, 1959 2 Sheets-Sheet 2 T I f4;

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ATTORNEYS United States Patent PAINT STRIPPING METHOD Dewey. M. Evans, Plymouth, Orlan M. Arnold, Grosse Pointe Park, and Francis G. Rylance, Farmington, Mich, assignors to Ajem Laboratories, Inc., Livonia, Mich.

Original application Sept. 3, 1959, Ser. No. 837,872, now Patent No. 3,109,439. Divided and this application Feb. 1, 1963, Ser. No. 264,464

1 Claim. (Cl. 13438) This application is a division of co-pending application Ser. No. 837,872, filed September 3, 1959, and now Patent Number 3,109,439. This invention relates to a paint stripping system and, more particularly, to a continuously operating system for stripping or removing from moving objects paint sprayed or otherwise accumulated thereon.

In the continuous production line manufacture of various machine parts, such as, for example, in the automobile industry, parts which are;to be painted or coated are moved in production line fashion more or less continuously past a paint spraying or applying station where the paint or other coating is applied. that some of the parts so painted are defective in some respect or the coating of paint improperly appliedso. that the defective parts are rejected at a subsequent inspection station and returned for re-painting or adjustment. After such adjustment or correction of the defectionand/ or prior to re-painting the part it may be desiredto strip therefrom the first applied coating.

Also, if such parts are carried continuously through the painting station on production line conveyors such as, for example, overhead monorail conveyors or other types of continuously moving supporting conveyors, the hooks or carriers or supporting members on the conveyor may accumulate a considerable amount of paint as they carrying the parts being painted through the paintingstation. Since the conveyor membersrepeatedly pass through the paint station, paint may accumulate on the conveyor members to a depth which interferes with the adequate hanging or supporting thereon, andthe accumulation of paint on the conveyor support may contaminate the part being conveyed in the vicinity of the contact therebetween with, accordingly, some discoloration or imperfections produced'on the part being painted, particularly when the part is being painted a different color. than was applied'to the part which that particular conveyor last conveyed through the painting station.

Kit is attempted to remove accumulations of paint from such conveying supporting members periodically, some shutdown of the conveyor operation is'required'as well as substantial man hours to accomplish the task. If on the other hand, it is attempted .to remove such accumulations chemically, it may be found that the requisite stripping baths are expensive and/or merely loosen or soften the accumulated paint requiring a substantialmanual removal and/or again require keeping the conveyor out of operation while'the conveyor members are soaked in or subjected to treatment by the chemical stripping material.

Also, in the treating of various parts other than painted thoroughly and automatically prior to assembly thereof in the ultimate device.

According to this invention, however, a system is provided for automatically stripping or cleaning paint or,

other materials from conveyor supports or parts carried by a continuously moving conveyor line or otherwise at the speed at which the conveyor moves, and as a COIItlIIU It may be, however,

3,231,424 Patented Jan. 25,, 1966 ous part of the conveyor or other operation so that the conveyor and/or parts carried thereby are maintained clean and stripped of paint and other soil. Furthermore, according to this invention, methods are provided for accomplishing this in substantially closed tanks to minimize any possible fire hazard and/or evaporation loss, and by combining dipping, scrubbing, spraying and. rinsing steps and techniques, the, conveyor and/or parts carried thereby are completely stripped of paint and dried within a relatively compact space and yet without stopping the conveyor, or slowing it down below the normal conveying operating speed thereof.

One objectv of this invention. is to. provide a system of the character described for continuously stripping from a continuously operating. conveyor and/ or parts carried thereby paint sprayed thereon, and for scrubbing and,

rinsing and drying the conveyor and partsat normal'opcrating conveyor speed.

Still another object of this invention is to providea system of thecharacter described for. continuously cleaning paint or other soil from continuously moving machine parts as they are moved. througha tank ofcleaning liquid and'for providing submerged jets for directing a scrubbing jet turbulence insaid liquid insaidtank against.

parts being conveyedtherethrough.

Still another object of this invention is, to provide a method of the character described for removing accumulations of paint from acontinuously moving conveyor without impeding the speed or continuous operation thereof and including the steps of immersing the conveyor in a stripping liquid, producing a forcefulagitation scrubbing action on the immersed conveyor in the stripping liquid, sprayingand. scrubbing the conveyor, after exiting fromthe stripping liquid to remove softened portions of FIG. 3 is. a vertical section along the line 3-3 of.

FIG: 1;

FIG. 4 is a vertical section along ,the line 4,4 of FIG. 1; and

FIG. 5 is a vertical section along the line 5-5 of.

FIG; 1.

Referring to the drawings in which like reference numbers denote like parts throughout the several views thereof, apparatus embodying this invention is illustrated for the stripping of'pai'nt from the pulleys and hooks of an overhead monorail conveyor the carrying rail of which is.

ind-icated'at 10 with a depending moving hook arrangement 11 depending therefrom and adapted in known man: ner, tomove continuously along rail 10 through a..pro-.

duction linefor carrying machine parts utiliz e'd'in the. production line: The stripping apparatus itself includes a number of sections which can be generally designated as an immersion tank section 12, a spray stripping section-13,-- arinsing section 14, and a drying section 15.

The embodiment of apparatus is illustrated here as applied to anoverhead monorail conveyor. Accordingly, the conveyor'enters the apparatus at the leftside of FIG. 1 at the normal overhead operating height of rail 10 through an entrance hoodsection 16.. For convenience in installation andmaintenance, however, the apparatus rests on the floor and, accordingly, rail 10' of the conveyor dips as indicatd in the drawing to the level of the immersion section 12. This immersion section 12 is essentially a closed tank of substantial longitudinal extent and containing the stripping liquid for softening and attacking paint which may have accumulated on conveyor hooks 11 and/ or parts carried thereby. Conveyor rail runs along the inside of the top of tank 12 as indicated in the drawings, and the level of liquid is maintained so as substantially to fill the immersion tank 12 and completely immerse conveyor hooks 11 as they pass through the immersion section from left to right in the drawings moving at the regular opera-ting speed of the conveyor.

' An offset tank 20 is provided adjacent the terminal end of immersion section 12 and in direct communication therewith. Mounted above this offset tank 20 is a centrifugal pump 21 driven by a motor 22 through a suitable drive indicated at 23. Preferably, centrifugal pump 21 is of the known variety that has a centrally located intake and a peripheral discharge, and pump 21 is mounted at a height such that the intake thereof is but slightly below the level of liquid in tank 20 so as to skim from the top of the liquid in tank 20 softened paint and other materials removed in the apparatus from hooks 11 passing therethrough.

Thus centrifugal pump 21 is provided as a skimming pump, for either continuous or intermittent operation as desired, to remove from the stripping liquid in the apparatus any paint or other material stripped therein from the monorail hooks 11. Atany convenient point along immersion section 12 a sludge separator 25 is provided of known construction to withdraw continuously or intermittently from immersion section 12 any paint or other materials stripped from the monorail hooks 11 which settles out from the liquid in the immersion section, instead of floating to the surface for removal thereof by skimming pump 21, it being understood that whether paint stripped from hooks 11 floats or settles out depends upon the composition thereof.

Also mounted above offset tank 20 is a centrifugal recirculating pump 30, driven by motor 31 through a suitable drive indicated at 32. Recirculating pump 30 takes the stripping liquid from offset tank 20 and, at substantial pressure, pumps it through a manifold 35 extending along and around the lower portion of immersion section 12 from whichmanifold the stripping liquid is discharged at substantial pressure and velocity through a plurality of nozzles 36, a substantial portion of which are inclined to direct the jet streams therefrom toward the left in the drawing and against the direction of travel hooks 11 for providing forceful agitation and physical scrubbing action of the stripping liquid in immersion section 12 against the advanced hooks 11. Others of the nozzles 36 are preferably directed transversely and/ or at different levels of immersion section 12 to enhance the agitation and scrubbing action and dispersion of paint stripped from hooks 11 to urge it either to float on the surface for skimming by pump 21 or to settle to the bottom for removal by sludge remover 25 or such other sludge remover or conveyor as may be provided.

Since many of the painting compositions and materials in the stripping liquid are quite volatile and obnoxious in various manners to varying degrees, exhaust blower devices indicated generally at 40 and 41, and driven respectively by motors 42 and 43, are provided at various points along immersion section 12, and particularly at the entrance and exit ends thereof, to withdraw therefrom and exhaust safely from the building obnoxious or dangerous fumes which may result from the strippingaction, the paint being stripped, or the stripping liquid. Such units at each end of the stripping trough also may provide an air curtain against escape of fumes into the room.

Furthermore, and particularly with volatile stripping liquid, a water seal is preferably provided in cases where the stripping liquid, although volatile, is heavier than and not readily miscible with water. That is, particularly as indicated in FIG. 3, a relatively thin layer 45 of water is maintained floating on the top surface of the stripping liquid to curtail the evaporation thereof. In such a case, objectionable disturbance of the interface between such water sealing layer and the stripping liquid is satisfactorily minimized by the provision of transverse baffles adjacent such interface and extending along substantially the entire length of immersion section 12 and across substantially the entire width thereof on either side of monorail 10. Thus hooks 11 may be carried through the stripping liquid and scrubbed with forceful agitation therein, but the effects of this movement and agitation on the water sealing layer 45 are interrupted and/or minimized by baffles 50. As noted above, some of the jet nozzles 36 from manifold 35 are directed to different levels in immersion section 12, and such of the nozzles 36 as may be directed upwardly provide for urging floating paint or other material removed from hooks 11 along the baflle 50 to the skimming pump to prevent undesirable accumulation of floating debris under baffles 50.

As will be understood, the particular length of immersion section 12 is correlated with the speed of conveyor hooks 11 as well as the strength or harshness of the stripping liquid to provide adequate contact or immersion time for softening and/or removal of the accumulation paint from hooks 11 by the immersion and scrubbing action in immersion section 12. At the exit end of immersion section 12, the monorail 10 rises to withdraw hooks 11 from the immersion in the stripping liquid and to guide them through spray stripping section 13 where a concentration of jet spray nozzles in manifold 35 deliver a violent spray against the hooks 11 as they emerge from the immersion section 12 for further mechanical scrubbing action to remove or strip therefrom accumulations of paint which may have been softened butnot completely removed during immersion in section 12. As will be noted from the drawing, material removed from hooks 11 in spray stripping section 13 will be returned along with the sprayed liquid back into the body of liquid in immersion section 12 to be removed therefrom either by skimming pump 21 or sludge separator 25.

From spray stripping section 13, hooks 11 are carried on monorail 10 into a rinsing section 14 where the hooks are sprayed, preferably by a rinsing liquid, to rinse therefrom any remaining paint not heretofore removed as well as the stripping liquid which may still be clinging thereto. As shown in the drawings rinsing section 14 includes an upper enclosed hood or covered tunnel part the Walls and top of which are preferably continuations with spray stripping section 13. Below tunnel 60 is a rinse liquid tank 61 from which rinse liquid is continuously withdrawn by pump 62, driven by motor 63 through a suitable drive 64, and pumped through manifold 65 from which it is ejected through jet spray nozzle 66 to impinge upon hooks 11 as they are carried through rinse section 14 on rail 10.

After being rinsed in rinse section 14, hooks 11 proceed on rail 10 to draining and drying section 15 including a closed tunnel portion 70 forming an enclosed continuation of tunnel 60. Here the hooks are subjected to the drying action of a stream of drying air, preferably heated, and supplied to drying section 15 by a conventional blower arrangement indicated at 71 as being driven by motor 72 through a suitable drive 73. From drying section 15 hooks 11 proceed on monorail 10 in cleaned and dried condition and ready to enter again the first station on the production line, to receive additional parts to be conveyed to a painting station, etc.

Satisfactory results have been obtained with this invention in the removal of paints such as are conventionally applied to automobile wheel discs, body parts, etc.e.g.,

'nitro-cellulose base lacquers, linseed oil or tung oil base paints, etc.by utilizing a system according to this invention in which the stripping liquid in immersion section 12 comprises trichloroethylene, perchloroethylene, or 1,1,1, trichloroethane and like solvents. Actually, with some paint materials, satisfactory results are obtained with a stripping liquid comprising a strong (e.g., about aqueous caustic solution as is used in conventional paint stripping operations, although the organic materials are preferred for most installations (with, of course, a covering layer of water 45) and particularly where the utilization of a more efiicient organic stripping liquid permits a shorter immersion time and, consequently, a shorter immersion section 12 in the apparatus. In some cases with types of paint or coating which are particularly difficult to remove (such as some Gilsonite chassis paint, and the like) a detergent-solvent stripping liquid is used of the type, for example, as is disclosed in the copending application of Arnold et al., S.N. 479,032, filed December 31, 1954, and assigned to the same assignee as the present application. This has matured as Patent No. 2,982,723.

Satisfactory results we obtained by using as a rinsing liquid in tank 61 for spray application in rinse section 14 clear water although, with some materials which are particularily diflicult to remove, a conventional aqueous detergent solution may be preferred.

It will accordingly be seen that, in a system embodying this invention, methods are provided for the continuous stripping for accumulations of paint or other materials from parts on a moving conveyor without impeding the continued operation or speed of the conveyor, and that provision is made for utilizing even highly volatile stripping and rinsing liquids with minimum evaporation losses and with avoidance of hazardous or obnoxious escape of the volatile materials into the area adjacent the stripping operation. Notwithstanding the provisions of means for forceful agitation and mechanical scrubbing action against the conveyor parts, a water layer seal may be provided over the surface of the stripping liquid, and materials stripped from the conveyor parts are continuously or intermittently removed from both the surface portion and lower portions of the stripping liquid.

As noted above, the foregoing considerations are also to be considered applicable to the cleaning of various machine parts, in addition to paint stripping, to remove therefrom various soils and residual compositions which may have been applied to or otherwise accumulated on the parts during stamping, extruding, drawing, bufi'ing, machining, etc., operations and, for example, prior to assembling these parts in the ultimate device or assembly for which they are intended. Utilizing a system in accordance with the foregoing, particularly including a closed tank through which the parts are moved submerged in a cleaning liquid, enhanced results are achieved from the standpoint of length of cleaning time and required space occupied by the cleaning apparatus. Also, as noted above, it is preferred to have at least some of the submerged jets 36 directed against the line of movement of the parts through the tank, and, preferably, positioned as close as possible to the parts being cleaned and to direct a jet of cleaning liquid tangentially to the surface of the part. Utilizing such arrangements, high liquid pressure can be provided in manifold 35 for forceful impingement through jets 36 on the parts being stripped or cleaned and substantially without disturbing or requiring intense agitation of the bulk of the cleaning liquid in tank 12.

While the methods and forms of apparatus herein described constitute a preferred embodiment of the invention, it is to be understood that the invention is not limited to these precise methods and apparatus, and that changes may be made therein without departing from the scope of the invention as defined in the accompanying claim.

What is claimed is:

In a method of stripping paint from hooks of a monorail conveyor used for carrying articles to be painted through a painting operation and for cleaning said hooks after an article has been painted thereon and prior to receiving a subsequent article to be painted, the steps which comprise submerging said hooks in an elongated cleaning solution bath adapted to soften said paint on said hooks, conveying said hooks on said monorail conveyor while submerged longitudinally through said cleaning solution bath for a substantial period of time, continuously withdrawing a portion of said cleaning solution from said bath for recirculation therein, recirculating said withdrawn cleaning solution into said bath through a plurality of submerged jets disposed in spaced relation substantially throughout the length of said bath and directed toward said hooks and against the direction of travel of said hooks through said bath forming a plurality of submerged jet streams of said cleaning solution impinging upon said submerged hooks and against said direction of travel thereof for direct scrubbing action against said submerged hooks, conveying said hooks out of said cleaning solution bath, spraying said hooks with a rinsing solution to rinse therefrom said cleaning solution and paint softened thereby, and drying said hooks for removing said rinsing solution without interruption of said continuous travel of said hooks along said monorail conveyor.

References Cited by the Exact UNITED STATES PATENTS 1,624,982 4/1927 Rosenberg 134109 X 2,389,488 11/1945 Dailey 13436 X 2,635,614 4/1953 Ford 134-74 X 2,689,198 9/1954 Judd 13431 X 2,710,818 6/1955 Winters 134-74 X 2,710,819 6/1955 Weber et al. 13434 X 2,838,289 6/1958 Northrup 2591 2,923,648 2/1960 KBurg 13412 3,033,712 5/1962 Brevik 13434 FOREIGN PATENTS 742,894 1/ 1956 Great Britain.

MORRIS O. WOLK, Primary Examiner.

DONALL H. SYLVESTER, Examiner. 

